Be Aware of Side Effects and Other Drug Interactions of Glaucoma Medications

By Amy Geiszler-Jones
Friday, April 24, 2020
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With older Americans being more at risk for glaucoma and that same population taking multiple prescription medications, it’s important for primary care physicians to understand the side effects and possible drug interactions of the various prescription glaucoma eye drops, says Anita Campbell, MD, a fellowship-trained glaucoma specialist with Grene Vision Group in Wichita.

According to the American Academy of Ophthalmology, people over age 60 are at an increased risk for glaucoma. People in that age demographic also take multiple prescriptions, according to a 2019 poll by the Kaiser Family Foundation, a nonprofit that tracks health issues. Nearly 90% of Americans ages 65 and older and nearly 75% of 50- to 64-year-olds take prescription drugs, the study found.

For this article, Dr. Campbell talks about four major classes of antihypertensive eye drops used to treat glaucoma and their potential side effects and interactions, which can be helpful for physicians in determining causes of certain symptoms or in prescribing drugs that can interact with glaucoma medication. As newer glaucoma drugs are being developed, new drug classes are being added to the glaucoma treatment arsenal, but they have fewer systemic side effects, Dr. Campbell said. Many glaucoma patients require treatment with eye drops in different classes.

Systemic side effects are more likely to occur if the patient doesn’t follow directions to facilitate the drop being absorbed in the eye. One minute of eyelid closure allows >90% ocular absorption. The remaining medication drains through the nasolacrimal duct into the vascular nasopharyngeal mucosa where systemic absorption can occur. Some sources recommend digital pressure near the bridge of the nose to prevent flow through the nasolacrimal duct, but it is hard for patients to find this landmark, so Dr. Campbell does not recommend it.

Alpha-2 Adrenergic Agonist

A commonly prescribed eye drop in this class is brimonidine, which decreases the production of intraocular fluid to reduce pressure. This drug may cause dizziness or dysequilibrium. Dr. Campbell avoids this medication in patients at risk of falls, such as the elderly or those using canes or walkers. The drug may also cause other symptoms such as lethargy, headaches and dryness in the mouth and nose.

Beta-Receptor Blockers

Timolol, one of the earliest eye drops prescribed to treat glaucoma, falls into this class. Drugs in this class also decrease the production of intraocular fluid, but also have the systemic risks of other beta blockers such as hypotension and bradycardia. It may affect a person’s exercise tolerance, “like hitting that wall quicker during a workout,” Dr. Campbell says. For patients with asthma or COPD, it can cause shortness of breath via bronchoconstriction. It may also increase depression symptoms. If it is necessary to prescribe a beta blocker for a patient with these underlying conditions, a cardioselective one such as carteolol is preferred.

Carbonic Anhydrase Inhibitors

This medication, which decreases production of intraocular fluid, is available in either eye drop form or pill form. Although drugs in this class contain nonantibiotic sulfonamides, only 10% of patients with a sulfa (antibiotic sulfonamide) allergy will have topical reactions because of the difference in metabolite form. However, those same patients cannot take acetazolamide in pill form, Dr. Campbell says. Other side effects with the pill form include kidney stones, upset stomach and frequent urination.

Prostaglandins

Drugs in this class increase intraocular fluid outflow and may cause changes to one’s iris color and longer eyelashes. Because the drug may cause inflammation, Dr. Campbell will avoid prescribing drugs in this class for those with inflammatory eye diseases such as iritis, uveitis or macular edema, but it’s less known whether it affects patients prone to inflammation elsewhere in the body.

Finding Alternatives

Physicians who suspect a glaucoma medication may be causing a patient’s symptoms should refer the patient back to his or her optometrist or ophthalmologist to consider alternative glaucoma treatments, Dr. Campbell says.

“It used to be hard to find alternatives, but now we can because we have so many classes and alternatives,” Dr. Campbell says.

She also advises that if allowed, hospitalized patients should use their outpatient prescribed glaucoma medications because hospital formularies are limited. This will help avoid glaucoma progression during inpatient stays.

Dr. Campbell is available for consultations on glaucoma medication interactions by contacting Grene Vision Group at 316-684-5158.

Clinical Trials Help Focus on Effective Glaucoma Surgeries

When Kansan Deborah Foy underwent surgery at Grene Vision Group last year to remove a cataract and relieve glaucoma pressure, she was part of a select group of patients nationwide in a clinical study about the safety and efficacy of the surgical system used to treat her glaucoma.

While those who practice medicine rely on clinical studies that help develop treatments and test the safety and effectiveness of drugs and therapies already approved by the FDA, not everyone who practices medicine participates in studies.

But that’s not the case at Grene Vision Group, a large, comprehensive provider of ophthalmology and optometry services that is headquartered in Wichita and has several locations throughout Kansas.

In the past two years, Grene Vision Group glaucoma specialist Anita Campbell, MD, has participated in two studies related to the long-term benefits of the OMNI Surgical System. The OMNI system has become one of the latest tools used in the growing list of minimally invasive glaucoma surgery (MIGS) procedures that have been transforming glaucoma treatment.

“It’s not experimental so it reassures people that it’s safe to be a part of. You’re helping further science, but not putting your eye at risk,” Dr. Campbell says about the efficacy studies for an FDA-cleared system.

The OMNI system received FDA clearance in January 2018, and Dr. Campbell started using the system not long after it became commercially available.

In the first study, which the OMNI manufacturer called Gemini, about 150 patients were enrolled, starting in March 2019, at several sites nationwide, including Grene Vision Group.

The OMNI surgical device combines two MIGS procedures. It removes part of the trabecular meshwork to allow direct drainage of the fluid buildup causing a rise in the ocular pressure, and it also injects viscoelastic fluid farther into the Schlemm’s canal to clear out the so-called pipes of the eye, which also improve pressure levels. It can be performed at the same time as cataract removal.

Dr. Campbell invited eligible patients who were already scheduled for both cataract surgery and OMNI glaucoma surgery to join the Gemini study. They were receiving the same treatment that had been recommended.

Foy was one of eight patients treated by Dr. Campbell who enrolled in the Gemini study. After failing an eye exam at her workplace, Foy had been referred for cataract removal surgery to Grene Vision Group. When the cataract surgeon realized Foy also was being treated with two different prescription eye drops to control her glaucoma, Foy was referred to Dr. Campbell for concurrent treatment of both ocular conditions.

“I needed the surgery and the study didn’t sound like a bad idea,” Foy says. While study subjects receive additional follow-up care and some financial compensation, that didn’t play a part in her decision to participate, Foy says.

“I just wanted to see again.”

With the Gemini study concluded, Sight Sciences has started enrolling subjects in another study that will look at the long-term benefits of the OMNIi system when used stand-alone for glaucoma treatment, Dr. Campbell says.

One patient who just joined the study said he was in a glaucoma drug study 25 years ago with another Grene Vision Group doctor and was excited to be asked to participate again, Dr. Campbell says.